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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id v11-20020a1709028d8b00b001cca8a01e68sm1840613plo.278.2023.11.30.12.51.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Nov 2023 12:51:21 -0800 (PST) From: Kees Cook To: Anders Larsen Cc: Kees Cook , Ronald Monthero , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v2 1/2] qnx4: Extract dir entry filename processing into helper Date: Thu, 30 Nov 2023 12:51:18 -0800 Message-Id: <20231130205120.3642477-1-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231130205010.it.412-kees@kernel.org> References: <20231130205010.it.412-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5530; i=keescook@chromium.org; h=from:subject; bh=DfWvLuw+1Lt1r34F/RNAIGyeJ3JO5Pv4v9kUKjoCgFA=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlaPXHlsbg/RAPaF3lRor/e48qn5raSb02XFsxv 4ZkTemLuR+JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZWj1xwAKCRCJcvTf3G3A Ju2FD/9yVnVUO73divQnIWrfkfSj+m1SuNrgcl/i1pzadtaT1HTZsGUv+Ya3kGmHdGQ6fKVnWXi AJn7Pxt6bDSI6Pnp7WwFOPBb50LY7rDQD8VIVpPCShrBa8JeJ8rq6g8STu1qmTtxV7T1JuiacGt 1b2ANdJqcUJJ8cMf5NSaFV/FhgOcihqgxKmKg80oK/N777WPtUHKsO/8X0epDkYWno5tpOxB4K/ EiofZJ8k0RZESvH42dGmA42jq4x/AkPusFHZ6T7oI6+GtzcgcMT5c4Qlh2kMelzZgqSsnkL5yPa WtKaqrom/6134zXVgWqqhQHwg2JPvdnZCWCaPq5Kvy7ERMBDM0bNtU35mIueySSSRdxRF8C9O7W bB5/orMoswd6pf0ksFbpvpGU/F0cCYDEMt/5cH6iM4d6XDbNaEj+o2utREOzfvGRZkNGSvV3rhh byj83Bl55pNV48ZVFGPhRJYI0hqGWqq7b5ZQebP6Je0KZQ2+g6SjaXjCh5fD7PIZrSuwFPubmj9 zp9ooNGudzBGisaj/ruuw5Zuw9bvB+rBbgcFyeUPaLYijtn4kVy/lX+6+yj/LIOf746oaO7TqTd xbns0Al2CLsr5HmW2BYYaNJhz1/SOKSiVb6fHGk9ilzv6MsBmow/kOy0uae+UB39OCG1LcWHl1J KxbuPyxHqnqro3A== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Both dir.c and namei.c need to perform the same work to figure out a directory entry's name and size. Extract this into a helper for use in the next patch. Cc: Anders Larsen Link: https://lore.kernel.org/r/20231118033225.2181299-1-keescook@chromium.org Signed-off-by: Kees Cook --- fs/qnx4/dir.c | 52 ++++++------------------------------------- fs/qnx4/qnx4.h | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 67 insertions(+), 45 deletions(-) diff --git a/fs/qnx4/dir.c b/fs/qnx4/dir.c index 66645a5a35f3..42a529e26bd6 100644 --- a/fs/qnx4/dir.c +++ b/fs/qnx4/dir.c @@ -15,43 +15,6 @@ #include #include "qnx4.h" -/* - * A qnx4 directory entry is an inode entry or link info - * depending on the status field in the last byte. The - * first byte is where the name start either way, and a - * zero means it's empty. - * - * Also, due to a bug in gcc, we don't want to use the - * real (differently sized) name arrays in the inode and - * link entries, but always the 'de_name[]' one in the - * fake struct entry. - * - * See - * - * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6 - * - * for details, but basically gcc will take the size of the - * 'name' array from one of the used union entries randomly. - * - * This use of 'de_name[]' (48 bytes) avoids the false positive - * warnings that would happen if gcc decides to use 'inode.di_name' - * (16 bytes) even when the pointer and size were to come from - * 'link.dl_name' (48 bytes). - * - * In all cases the actual name pointer itself is the same, it's - * only the gcc internal 'what is the size of this field' logic - * that can get confused. - */ -union qnx4_directory_entry { - struct { - const char de_name[48]; - u8 de_pad[15]; - u8 de_status; - }; - struct qnx4_inode_entry inode; - struct qnx4_link_info link; -}; - static int qnx4_readdir(struct file *file, struct dir_context *ctx) { struct inode *inode = file_inode(file); @@ -74,26 +37,25 @@ static int qnx4_readdir(struct file *file, struct dir_context *ctx) ix = (ctx->pos >> QNX4_DIR_ENTRY_SIZE_BITS) % QNX4_INODES_PER_BLOCK; for (; ix < QNX4_INODES_PER_BLOCK; ix++, ctx->pos += QNX4_DIR_ENTRY_SIZE) { union qnx4_directory_entry *de; + const char *fname; offset = ix * QNX4_DIR_ENTRY_SIZE; de = (union qnx4_directory_entry *) (bh->b_data + offset); - if (!de->de_name[0]) - continue; - if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK))) + fname = get_entry_fname(de, &size); + if (!fname) continue; + if (!(de->de_status & QNX4_FILE_LINK)) { - size = sizeof(de->inode.di_fname); ino = blknum * QNX4_INODES_PER_BLOCK + ix - 1; } else { - size = sizeof(de->link.dl_fname); ino = ( le32_to_cpu(de->link.dl_inode_blk) - 1 ) * QNX4_INODES_PER_BLOCK + de->link.dl_inode_ndx; } - size = strnlen(de->de_name, size); - QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, name)); - if (!dir_emit(ctx, de->de_name, size, ino, DT_UNKNOWN)) { + + QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, fname)); + if (!dir_emit(ctx, fname, size, ino, DT_UNKNOWN)) { brelse(bh); return 0; } diff --git a/fs/qnx4/qnx4.h b/fs/qnx4/qnx4.h index 6283705466a4..5c2b1fb6b952 100644 --- a/fs/qnx4/qnx4.h +++ b/fs/qnx4/qnx4.h @@ -44,3 +44,63 @@ static inline struct qnx4_inode_entry *qnx4_raw_inode(struct inode *inode) { return &qnx4_i(inode)->raw; } + +/* + * A qnx4 directory entry is an inode entry or link info + * depending on the status field in the last byte. The + * first byte is where the name start either way, and a + * zero means it's empty. + * + * Also, due to a bug in gcc, we don't want to use the + * real (differently sized) name arrays in the inode and + * link entries, but always the 'de_name[]' one in the + * fake struct entry. + * + * See + * + * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6 + * + * for details, but basically gcc will take the size of the + * 'name' array from one of the used union entries randomly. + * + * This use of 'de_name[]' (48 bytes) avoids the false positive + * warnings that would happen if gcc decides to use 'inode.di_name' + * (16 bytes) even when the pointer and size were to come from + * 'link.dl_name' (48 bytes). + * + * In all cases the actual name pointer itself is the same, it's + * only the gcc internal 'what is the size of this field' logic + * that can get confused. + */ +union qnx4_directory_entry { + struct { + const char de_name[48]; + u8 de_pad[15]; + u8 de_status; + }; + struct qnx4_inode_entry inode; + struct qnx4_link_info link; +}; + +static inline const char *get_entry_fname(union qnx4_directory_entry *de, + int *size) +{ + /* Make sure the status byte is in the same place for all structs. */ + BUILD_BUG_ON(offsetof(struct qnx4_inode_entry, di_status) != + offsetof(struct qnx4_link_info, dl_status)); + BUILD_BUG_ON(offsetof(struct qnx4_inode_entry, di_status) != + offsetof(union qnx4_directory_entry, de_status)); + + if (!de->de_name[0]) + return NULL; + if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK))) + return NULL; + if (!(de->de_status & QNX4_FILE_LINK)) + *size = sizeof(de->inode.di_fname); + else + *size = sizeof(de->link.dl_fname); + + *size = strnlen(de->de_name, *size); + + return de->de_name; +}